Magnetic linear drive

ABSTRACT

The invention relates to a magnetic linear drive comprising a base. A first displaceable part can be displaced in relation to the base. A second displaceable part is mounted on the first displaceable part. Both the first displaceable part and the second the second displaceable part can be displaced along an axis. A contact piece of a medium or high-voltage switch can be displaced by means of the movement of the first displaceable part and the second displaceable part.

CLAIM FOR PRIORITY

This application claims the benefit of priority to German ApplicationNo. 10313144.2 which was filed in the German language on Mar. 17, 2003,the contents of which are hereby incorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The invention relates to a magnetic linear drive, and in particular, toa magnetic linear drive having a base and a first movable part.

BACKGROUND OF THE INVENTION

One such magnetic linear drive is known, for example, from the SwissPatent Specification CH 184 977. The known linear drive has a pluralityof windings, into which an armature is drawn when current flows throughthe windings. The known armature is formed in a number of parts, witheach part of the armature being mounted in a guide sleeve which is ineach case attached to the magnet housing and to the pole shoes. Theindividual parts of the armature can be moved relative to one another,but only by a certain amount, which is governed by an air gap. Amovement of the individual parts of the armature is in each caseprovided, in the form of a chain, in a fixed sequence in order to omit amovement to an element that is to be driven.

The movement which can be tapped off from the known drive can take placeonly on the basis of a single pattern, which is fixed and ispredetermined by the design. Flexible use of the drive is thus possibleonly to a restricted extent. Furthermore, the armature must be assembledfrom a very large number of individual parts in order to achieve a largelinear movement, so as to produce a correspondingly large number of airgaps between the individual parts and to produce a large linear movementoverall.

A further magnetic linear drive is known, for example, from EuropeanPatent Specification EP 0 830 699 B1. The arrangement has a coil throughwhich a current can flow. A drive rod is moved by the magnetic fieldoriginating from the coil, using the force effects on permeable boundarysurfaces. The drive rod enters the interior of the coil in the process.

The force effect on the movable part changes depending on the depth towhich the drive rod enters the coil. The linear movement of a lineardrive such as this is restricted.

SUMMARY OF THE INVENTION

The invention relates to a magnetic linear drive having a base andhaving a first movable part, which can be moved along an axis, wherein afirst magnetic force effect for movement of the first movable part canbe produced between the base and the first movable part, and a secondmagnetic force effect for movement of the second movable part can beproduced between the first movable part and a second movable part whichcan be moved along the axis.

The present invention discloses a magnetic linear drive of the typementioned initially such that the movement sequence can be controlledeasily, with the movable part having a long linear movement, and asuitable method for operation of a magnetic linear drive such as this.

According to the invention, a magnetic linear drive has a second movablepart being mounted such that it can move on the first movable part.

The provision of two movements of two parts which can be movedindependently of one another makes it easier to control a movementsequence. A large number of movement profiles can be created byacceleration or deliberate braking of in each case one of the movableparts or corresponding superimposition of the movements of the twomovable parts. Furthermore, it is also possible to drive one of themovable parts, so that the magnetic linear drive can produce a limitedlinear movement. Furthermore, the splitting into linear movementelements of a first movable part and of a second movable part makes itpossible to produce a better force profile throughout the entiremovement. The magnetic forces which can be produced between the firstmovable part and the second movable part, as well as between the baseand the first movable part, can each be produced independently of oneanother. The total force requirement for a movement can thus bedistributed between a plurality of elements. The magnitude and timeprofile of any force effect can thus be optimized per se, withoutdirectly influencing the other force effect at the same time. Overall,the two magnetic force effects complement one another to form aresultant force effect. A magnetic linear drive such as this can be usedas a drive for a medium-voltage or high-voltage switch, in particularfor a circuit breaker.

Magnetic force effects can be produced, for example, by a combination ofcoils through which a current flows, permanent magnets andhigh-permeability material. Magnetic force effects can easily be matchedto the technical requirements. Robust mechanical structures, which aresubject to only a small amount of mechanical wear, can in this case bechosen in order to transmit the forces.

Mounting the second movable part on the first movable part makes itpossible to couple the movements of the movable parts to one another ina simple manner. The second movable part can be repelled from the firstmovable part and can thus be moved in a simple manner either at the sametime as the first part or at a time after or before any movement of thefirst part. In comparison to known designs, this makes it possible toproduce a sufficiently large force effect over the entire movementdistance of the entire movement, with an increased linear movement.

Furthermore, it is advantageously possible to provide for a first and asecond permanent magnet to be aligned with respect to one another insuch a way that, in a limit position of the magnetic linear drive, themagnetic fluxes of the first permanent magnet and of the secondpermanent magnet are closed along a common path within ahigh-permeability multiple part core body.

The use of permanent magnets to secure the positions means that there isno need for mechanical latches for the magnetic linear drive. If thelines of force which originate from the permanent magnet are combinedalong a common path, then the holding force which originates from one ofthe permanent magnets is increased. In comparison to a single permanentmagnet which produces an increased magnetic force, a plurality ofmagnetically coupled permanent magnets have the advantage that they canbe arranged distributed along a preferred path. It is thus possible todeliberately influence the closed path within a high-permeability corebody and to define more precisely the routing of the magnetic flux.

It is advantageously also possible to provide for the field windings tobe arranged at a rigid angle with respect to the first movable part.

Arranging the field windings on the first movable part at a fixed angleallows the field windings, which are intended to be driven electrically,to be concentrated on a single part. It is thus possible for the baseand the second movable part not to have to have any field windings whichhave to be driven electrically. This simplifies the design of a magneticlinear drive such as this.

It is also possible to provide for the second movable part to be aplunger-type armature.

For specific applications of a magnetic linear drive, for example fordriving contact pieces in a medium-voltage or high-voltage circuitbreaker, it may, for example, be possible to provide for the movementwhich is produced by the first movable part to be used for movement ofthe contact pieces, and for the movement of the second movable part tobe used for compression of a contact-pressure element, which produces acontact-pressure force on the contact pieces of the circuit breaker. Thepower which is required to produce the contact-pressure force can beproduced by means of a simple plunger-type armature. The plunger-typearmature is extremely robust, and is virtually free of mechanical wear.

A further advantageous embodiment can provide for each of the movableparts to have an associated field winding.

A movement sequence can be controlled in a simple manner by theassociation of field windings with each of the movable parts. The forceand movement profiles of each of the movable parts can easily becontrolled by the design of the field winding, for example by varyingthe number of turns. The force effects which can be produced between thefirst moving part and the base, as well as between the first moving partand the second moving part, can thus be adjusted and varied in a simplemanner.

Another embodiment of the invention is a method for operation of amagnetic linear drive, which has at least some of the features describedabove.

A first method provides that during any movement of at least one of themovable parts, a magnetic circuit which is fed jointly by a firstpermanent magnet and a second permanent magnet is separated within ahigh-permeability multiple part body into magnetic circuits which arefed separately.

The joint feed to a magnetic circuit from a first and a second permanentmagnet on the one hand allows a very high holding force to be producedby the magnetic coupling of two permanent magnets. On the other hand,once the permanent magnets have been separated, they can each be used intheir own right to produce holding forces which act independently of oneanother. For example, depending on the position of the magnetic lineardrive, it is possible to produce increased holding forces in onespecific position, and for lower holding forces to be required inanother position.

A further method specifies that the time sequence of the movements ofthe first and of the second movable part is influenced by means of acontrol apparatus, using at least one of the field windings.

A field winding which is deliberately driven makes it possible todeliberately strengthen or to deliberately weaken the forces which occurwithin the magnetic linear drive. This makes it possible to adapt theforce effects of the field windings which are provided for driving themovable parts, without any mechanical intervention in the system. Thefield winding which is driven by means of the control apparatus can thusbe used to produce additional acceleration forces or a braking effect.In this case, it is possible to provide for one and the same fieldwinding to be used to drive one movable part during a movement sequence,and for the drive to be provided by a control apparatus during anothermovement sequence, in order to produce a braking or acceleratingmagnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following textwith reference to exemplary embodiments, which is illustratedschematically in a drawing, and in which:

FIGS. 1 to 3 show a movement sequence of a magnetic linear drive from anoff position to an on position.

FIGS. 4 to 6 show the magnetic linear drive being moved from an onposition to an off position.

DETAILED DESCRIPTION OF THE INVENTION

The design of a magnetic linear drive 1 will be described with referenceto FIG. 1. The magnetic linear drive 1 has a base 2. The base 2 is partof a high-permeability multiple part core body, and is arranged in afixed position on guide rods 3 a, 3 b. The guide rods 3 a, 3 b aresupported on a base plate 4. The guide rods 3 a, 3 b extend parallel toan axis 5. The magnetic linear drive 1 is formed essentially co-axiallywith respect to the axis 5, but may also be formed with mirror-imagesymmetry on a plane. A first movable part 6 is arranged such that it canbe moved longitudinally along the axis 5 on the guide rods 3 a, 3 b. Thefirst movable part 6 is likewise part of the high-permeability corebody. The first movable part 6 (with a bold surround) has a recess inwhich the base 2 engages, so that the longitudinal movement capabilityof the first movable part 6 along the guide rods 3 a, 3 b is limited.The movable part 6 has a first field winding 7, a second field winding 8and a third field winding 9. The field windings 7, 8, 9 each have alarge number of turns which surround the axis 5. Ideally, the fieldwindings 7, 8, 9 are arranged coaxially with respect to the axis 5. Afirst permanent magnet 10 is arranged between the first field winding 7and the second field winding 8. A second permanent magnet 11 is arrangedbetween the second field winding 8 and the third field winding 9. Thefirst permanent magnet 10 and the second permanent magnet 11 may in thiscase be in the form of different design embodiments. For example, theymay each extend in an annular shape around the axis 5 or may be formedfrom a large number of magnet elements, whose overall effect in eachcase results in a first and a second permanent magnet. Both the firstpermanent magnet 10 and the second permanent magnet 11 are in this casemagnetized and arranged in such a way that the magnetization directionsof the permanent magnets 10, 11 run radially with respect to the axis 5.In the area of the second field winding 8 and of the third field winding9, the movable part 6 has a recess through which the second fieldwinding 8 and the third field winding 9 pass. A plunger-type armature 12is mounted such that it can move in the recess. The plunger-typearmature 12 represents a second movable part. The plunger-type armature12 is connected at a rigid angle to a drive rod 13, which is mounted onthe first movable part 6 such that it can move along the axis 5. Thedrive rod 13 is coupled to a movable contact piece 14 of an electricalcontact arrangement. A contact arrangement such as this is, for example,a medium-voltage or high-voltage circuit breaker. The drive rod 13 iscoupled to the movable contact piece 14 with the interposition of acompression element 15. An arrangement having a plurality of compressionsprings 16 a, b is provided between the base plate 4 and the firstmovable part 6 in order to damp a switching-off movement and in order tosupport a switching-on movement. The compression springs 16 a, b areoptional elements.

A process for switching on the magnetic linear drive 1 will be describedin exemplary form in the following text with reference to FIGS. 1, 2 and3. When the magnetic linear drive 1 is in the off position, the magneticlines of force which originate from the first permanent magnet 10 andfrom the second permanent magnet 11 form a common magnetic circuit (seeFIG. 6). The common magnetic circuit in this case passes through amultiple part core body which comprises parts of the base 2, parts ofthe first movable part 6, and parts of the plunger-type armature 12. Thesections in which a magnetic flux is intended to be carried are eachformed from high-permeability material. The coupling of the magneticfields of the first permanent magnet 10 and of the second permanentmagnet 11 results in an increased holding force of the first movablepart 6 on the base 2, and of the plunger-type armature 12 on the firstmovable part 6. A direct current is caused to flow through the firstfield winding 7 in a first direction in order to produce a first forceeffect between the base 2 and the first movable part 6 (FIG. 1). Thefirst direct-current direction in this case be chosen so as to increasethe magnetic flux originating from the first permanent magnet 10. Thismeans that the magnetic circuit, which was previously fed jointly fromthe first permanent magnet 10 and the second permanent magnet 11, ischanged to a non-equilibrium state, so that a force effect is producedbetween the first movable part 6 and the base 2. This force effectresults in closure of a gap 17 between the base 2 and the first movablepart 6. At the same time, a further gap 18 is opened (see FIG. 1, afterFIG. 2). The production of the further gap 18 breaks the jointly fedmagnetic circuit within the multiple part high-permeability core body,and each of the permanent magnets 10, 11 feeds a separate magnet circuitwithin a high-permeability core body (see FIG. 2). In order to cause theplunger-type armature 12 to move, current must likewise be passedthrough the third field winding 9 in a first direction. The force effecton the high-permeability boundary surfaces results in a movement of theplunger-type armature 12, and the magnetic gap 19 is closed (see FIG. 2after FIG. 3). The linear movement of the plunger-type armature 12 movesthe movable contact piece 14 to its on position. Furthermore, thecompression element 15 is compressed and, as a result of the forceeffect of the compression element 15, the movable contact piece 14 ispressed with the necessary contact-pressure force against a matingcontact piece. In the on position (FIG. 3), the first permanent magnet10 produces a holding force between the first movable part 6 and thebase 2. The second permanent magnet 11 produces a holding force betweenthe plunger-type armature 12 and the first movable part 6.

The movement of the magnetic linear drive 1 from an on position to anoff position will be described in the following text with reference toFIGS. 4, 5 and 6. Direct current has to flow in a second directionthrough the second field winding 8 in order to produce a switching-offmovement. The direct current in this case be in such a direction thatthe magnetic fluxes which originate from the two permanent magnets arereinforced, thus assisting and promoting the production of a commonmagnetic circuit from the first permanent magnet 10 and the secondpermanent magnet 11. The magnetic force effect between the movable part6 and the base 2 results in a reduction in the size of the further gap18. Furthermore, the magnetic gap 19, which is now located in the areaof the second field winding 8, is likewise closed. To produce aswitching-off movement, current flows through the second field winding8. The plunger-type armature 12 and the first movable part 6 then movevirtually at the same time. In order to co-ordinate the movementsequence of the movement of the first movable part 6 and of theplunger-type armature 12, it is optionally possible to provide forcurrent likewise to be passed through the third field coil 9 in a seconddirection, by means of a control apparatus. This reinforces the forceeffect on the plunger-type armature 12, since a magnetic field in theopposite direction to that of the second permanent magnet 11 weakens themagnetic field from the permanent magnet 11, and thus reduces theholding forces between the plunger-type armature 12 at the first movablepart 6. This forces the plunger-type armature 12 to move before anymovement of the first movable part 6 (see FIG. 4, after FIG. 5). Oncethe first movable part has also been moved to its off position as aresult of current flowing through the second field winding 8, themagnetic lines of force which originate from the first permanent magnet10 and from the second permanent magnet 11 complement one another toform a common magnetic circuit, which is formed in the high-permeabilitymaterial of one of the plunger-type armature 12, the first movable part6 or the base 2. The common magnetic circuit holds the first movablepart 6 firmly on the base 2, and holds the plunger-type armature 12firmly on the first movable part 6.

1. A magnetic linear drive comprising: a base; and a first movable part,which can be moved along an axis, wherein a first magnetic force effectfor movement of the first movable part is produced between the base andthe first movable part, and a second magnetic force effect for movementof a second movable part is produced between the first movable part andthe second movable part, which can be moved along the axis, wherein thesecond movable part is mounted such that it can move on the firstmovable part.
 2. The magnetic linear drive as claimed in claim 1,further comprising a first and a second permanent magnet aligned withrespect to one another such that, in a limit position of the magneticlinear drive, the magnetic fluxes of the first permanent magnet and ofthe second permanent magnet are closed along a common path within ahigh-permeability multiple part core body.
 3. The magnetic linear driveas claimed in claim 1, further comprising field windings arranged at afixed angle with respect to the first movable part.
 4. The magneticlinear drive as claimed in claim 1, wherein the second movable part is aplunger-type armature.
 5. The magnetic linear drive as claimed in claim1, wherein each of the movable parts has an associated field winding. 6.A method for operation of a magnetic linear drive having a base and afirst movable part, which can be moved along an axis, wherein a firstmagnetic force effect for movement of the first movable part is producedbetween the base and the first movable part, and a second magnetic forceeffect for movement of a second movable part is produced between thefirst movable part and the second movable part, which can be moved alongthe axis, wherein the second movable part is mounted such that it canmove on the first movable part, comprising separating a magnetic circuitwhich is fed jointly by a first permanent magnet and a second permanentmagnet within a high-permeability multiple part body into magneticcircuits which are fed separately, during movement of at least on of themovable parts.
 7. A method for operation of a magnetic linear drivehaving a base and a first movable part, which can be moved along anaxis, wherein a first magnetic force effect for movement of the firstmovable part is produced between the base and the first movable part,and a second magnetic force effect for movement of a second movable partis produced between the first movable part and the second movable part,which can be moved along the axis, wherein the second movable part ismounted such that it can move on the first movable part, comprisinginfluencing the time sequence of the movements of the first and of thesecond movable part by means of a control apparatus, using at least oneof the field windings.